So, the core of my problem is that I might not know what the thing I want is called. I think it's called "metadata", but Google doesn't turn up anything. Anyway when you type a function's name in WebStorm (though I can not imagine this being unique to it) it will sometimes display a tooltip, telling you what the function does and what parameters it takes- this really cuts down the time needed to look stuff up. So, I want to bundle those with the functions I write. How do I do that, or at least what is it properly called?
There isn't one term for it, unfortunately. Microsoft's term is "IntelliSense." Various other terms are listed in this answer on programmers.stackexchange.com:
I believe the term they use at JetBrains (the people behind WebStorm and IntelliJ and such) is "Code Completion," based on the WebStorm help.
More about WebStorm code completion on their blog. It looks like they'll work from the source code, using JSDoc if they find it.